Travel time reliability is a fundamental factor in travel behavior. It represents the temporal uncertainty experienced by users in their movement between any two nodes in a network. The importance of the time reliability depends on the penalties incurred by the users. In road networks, travelers consider the existence of a trip travel time uncertainty in different choice situations (departure time, route, mode, and others). In this paper, a systematic review of the current state of research in travel time reliability, and more explicitly in the value of travel time reliability is presented. Moreover, a meta-analysis is performed in order to determine the reasons behind the discrepancy among the reliability estimates.

Value of Travel Time Reliability: A Review of Current Evidence

High demands for broadband mobile wireless communications and the emergence of new wireless multimedia applications constitute the motivation to the development of broadband wireless access technologies in recent years. The Long Term Evolution/System Architecture Evolution (LTE/SAE) system has been specified by the Third Generation Partnership Project (3GPP) on the way towards fourth-generation (4G) mobile to ensure 3GPP keeping the dominance of the cellular communication technologies. Through the design and optimization of new radio access techniques and a further evolution of the LTE systems, the 3GPP is developing the future LTE-Advanced (LTE-A) wireless networks as the 4G standard of the 3GPP. Since the 3GPP LTE and LTE-A architecture are designed to support flat Internet Protocol (IP) connectivity and full interworking with heterogeneous wireless access networks, the new unique features bring some new challenges in the design of the security mechanisms. This paper makes a number of contributions to the security aspects of the LTE and LTE-A networks. First, we present an overview of the security functionality of the LTE and LTE-A networks. Second, the security vulnerabilities existing in the architecture and the design of the LTE and LTE-A networks are explored. Third, the existing solutions to these problems are classically reviewed. Finally, we show the potential research issues for the future research works.

A Survey on Security Aspects for LTE and LTE-A Networks

Handoff is a key element in wireless cellular networks in order to provide quality of service (QoS) to the users and to support users' mobility. Handoff failure will result in the forced termination of an ongoing call. From the user's point of view, the service of a handoff request is more important, as the forced termination of an ongoing call is more annoying than the blocking of new calls. Therefore, in order to support QoS to the users and to provide ubiquitous coverage, the handoff procedure ought to be further investigated. This paper provides a comprehensive survey of the basic elements, the different types and phases of the handoff procedure. Moreover, particular interest has been given in the horizontal handoff execution phase by discussing and classifying the most recent handoff prioritization schemes into categories based on the concepts that these schemes adopt, e.g. channel reservation, handoff queueing, channel transferred, subrating, genetic and hybrid schemes and in the vertical handoff decision phase by presenting different decision algorithms.

Handoff prioritization and decision schemes in wireless cellular networks: a survey

The user mobility pattern (UMP) scheme is introduced for location update and paging in wireless systems where mobile terminals (MTs) maintain their history data in a database called user mobility history (UMH). During a location update, a UMP is derived from UMH and registered to the network. Unless the MT detects that it has moved out of the registered UMP, it does not perform any other location update. On the other hand, cells are paged selectively according to the cell entry times in the registered UMP upon a call arrival for the MT. The related data structures and the protocols for the UMP scheme are presented in the paper. The experimental results show that the UMP scheme outperforms the time-based and movement-based location update schemes as well as the blanket, selective, and velocity paging schemes.

http://delab.csd.auth.gr/~dimitris/courses/mpc_fall05/papers/location_management/01081758.pdf

User mobility pattern scheme for location update and paging in wireless systems

Locating mobile users and devices efficiently is a critical operation in cellular networks. This is done using a combination of location update(by the mobile) and paging (by the network). The paging scheme determines how and where to search for a mobile user given the latestlocation update information from that user. In this paper, we considerhow to increase the efficiency of the paging scheme.Much previous work has relied on simulation or modeling to design and evaluate the performance of proposed paging schemes. We take a different, data-driven approach in how we design and evaluate our solution. Specifically, we mine more than 300 million call records from a large cellular operator to characterize user mobility and create mobility profiles. We then develop a family ofprofile-based paging techniques, considering both static schemes and dynamic schemes which adapt as user profiles continuously get updated. We find that our paging techniques can dramatically reducesignaling load (up to 80%) with minimal increase in paging delay (usually less than 10%).

http://jeanbolot.com/Mobicom2007mobility.pdf

Mining call and mobility data to improve paging efficiency in cellular networks

On the problem of location update and terminal paging, many schemes using ring-paging strategies have been proposed. However, sequentially paging the rings surrounding the mobile user's last updated location may cause large paging cost. We propose a direction-based location update (DBLU) scheme using a line-paging strategy to reduce the paging cost. A moving direction identification mechanism using only simple computations detects the change of moving direction and updates the mobile's location. The numerical results show that our DBLU scheme achieves good performance when the paging cost is high.

/pdf/a-direction-based-location-update-scheme-with-a-line-paging-3fold7pcx1.pdf

A direction-based location update scheme with a line-paging strategy for PCS networks

Universal Mobile Telecommunications System (UMTS) supports Internet protocol (IP) multimedia services through IP multimedia core network subsystem (IMS). Since the IMS information is delivered through the general packet radio service (GPRS) transport network, a UMTS mobile station (MS) must activate GPRS packet data protocol (PDP) context before it can register to the IMS network. In the Third-Generation Partnership Project (3GPP) specifications, authentication is performed at both the GPRS and the IMS networks before an MS can access the IMS services. We observe that many steps in this 3GPP "two-pass" authentication procedure are identical. Based on our observation, this paper proposes an one-pass authentication procedure that only needs to perform GPRS authentication. At the IMS level, authentication is implicitly performed in IMS registration. Our approach may save up to 50% of the IMS registration/authentication traffic, as compared with the 3GPP two-pass procedure. We formally prove that the one-pass procedure correctly authenticate the IMS users.

https://ir.nctu.edu.tw:443/bitstream/11536/13652/1/000229649600010.pdf

One-pass GPRS and IMS authentication procedure for UMTS

The problem of diagnosis and spare allocation for random-access memory (RAM) with coupling faults is addressed. A number of spare allocation algorithms for RAM with row and column redundancy have recently been proposed. These procedures, however, have been restricted to repair stuck-at faults. The authors examine both diagnosis and repair of coupling faults in RAMs utilizing spare rows and columns. It is shown that a coupling fault is repaired if its coupling cell is replaced by utilizing a spare row or its coupled cell is replaced by utilizing a spare row or column. By specifying both the coupled cell and coupling cell, the amount of redundancy required to repair a given set of faults may be reduced. A diagnosis procedure for RAM is provided to locate stuck-at faults as well as coupling faults. A graph model is used to describe the repair of coupling faults. A repair procedure has been implemented to allocate rows and columns for repair. >

Diagnosis and repair of memory with coupling faults

Diagnosis strategies are investigated for repairable VLSI and WSI structures based on integrated diagnosis and repair. Knowledge of the repair strategy, the probability of each unit being good, and the expected test time of each unit is used by the diagnosis algorithm to select units for testing. The general problem is described, followed by an examination of a specific case. For k-out-of-n structures, a complete proof is given for the optimal diagnosis procedure of Y. Ben-Dov (1981). A compact representation of the optimal diagnosis procedure is described, which requires O(n/sup 2/) space and can be generated in O(n/sup 2/) time. Simulation results are provided to show the improvement in diagnosis time over online repair and offline repair. >

Ming-Feng Chang

Papers

A direction-based location update scheme with a line-paging strategy for PCS networks

One-pass GPRS and IMS authentication procedure for UMTS

Diagnosis and repair of memory with coupling faults

Optimal diagnosis procedures for k-out-of-n structures

Pragmatic real-time logistics management with traffic IoT infrastructure: Big data predictive analytics of freight travel time for Logistics 4.0